Many such apparatus have a plurality of roller shafts which are arranged in parallel to one another in a frame, with a common drive mechanism for the roller shafts and with a respective friction clutch between the drive mechanism and the individual roller shafts. The friction clutch substantially comprises two clutch elements, each of which has a friction surface and which are each in driving connection with the drive mechanism and the respective roller shaft. A pressure device presses the friction surfaces of the clutch elements against one another.
An apparatus of the above type has been disclosed, for example, by U.S. Pat. No. 4,325,474. In this apparatus, at their ends the parallel roller shafts bear sprocket wheels which are driven by a common chain. A friction clutch is provided between the sprocket wheel and the roller shaft and the two parts of the clutch elements are pressed against one another by a spring.
In the case of transport apparatus comprising such roller shafts, the goods to be conveyed are either arranged directly on the roller shafts or the roller shafts bear pallets for the goods to be conveyed. The goods to be conveyed are optionally periodically halted, and in order to avoid friction phenomena at the periphery of the conveying rollers, friction clutches are arranged between the common drive mechanism and the roller shafts, which friction clutches are generally adjustable and permit sliding above a specific torque.
U.S. Pat. No. 4,819,787 describes another transport apparatus for the same purpose. In this design a longitudinal shaft is provided and the individual friction clutches are arranged thereon. An angle gear, namely a friction gear, is arranged between the driven clutch element of the friction clutch and the roller shaft.
In order to produce the driving force, friction clutches of the known type employ springs which, for example, have the form of helical springs and embrace the drive shaft. In many designs the springs also transmit the torque. The replacement of fatigued or fractured springs is complicated, particularly when these surround the drive shaft.